You're exactly right, it is butted into the 4 by 4 against the house instead of sitting on top of it and that is exactly the problem. It is weight bearing and yet somehow for over 100 years it has not collapsed. The only thing that I can imagine is they have some long ass lags coming through the back side. By cantilevered I was referring to how far it sticks off the house, you are technically correct however. Nice catch.